1. Field of the Invention
The present invention relates to an actuator system and a vibration testing method used for evaluating characteristics of a structure which influences an earthquake response or for proving the strength and reliability of the structure by applying a deformation and a load to the structure. More particularly, it relates to a vibration testing device and a method for evaluating a vibration response suitable for a huge structure.
2. Description of the Related Art
A structure is required to be designed so as to have sufficient strength to a load which may be applied to the structure during its use. For example, for building and civil engineering structures, it is important to design them so as to have the sufficient strength to the severest earthquake that may take place during their use. Therefore, a vibration test is carried out to examine a vibration response of the structure itself to the earthquake or to test characteristics of members which influence the earthquake response. For the vibration test, various methods have been proposed. In one method thereof, a deformation or a load which is supposed to be generated at the earthquake is applied to the structure or its members by an actuator to examine a response, a damage state, etc. generated at this time.
In a particular case of the actuator suitable for a large-sized structure, the so-called hybrid experiment techniques have been proposed in which a numerical simulation and a vibration test are combined to reproduce the same vibration state as in the case that a test piece is actually used. One of the above techniques is disclosed in, for example, JP-A-60-13240. Besides, U.S. Pat. No. 5,388,056 discloses an apparatus and a method for carrying out the hybrid experiment technique in real time.
Furthermore, JP-A-9-79939 and JP-A-10-206304 disclose techniques for cooperatively using a plurality of actuators in remote places. These publications disclose constitutions in which a computer as a host sends command signals through a network to drive the actuators at the remote places.
In the case of a huge structure, a part to be subjected as a test piece to the vibration test is also large. Moreover, a plurality of parts of the large structure are often tested. It is difficult from the economical viewpoint that one experimental facility holds an experimental device suitable for the vibration test for such a huge structure. Therefore, it is desirable that one experiment can be performed by cooperatively using the experimental devices in separate experimental facilities that are not always near to one another. Besides, in the case that the numerical simulation is burdened with a heavy load, it is desirable to use a high-performance computer such as a supercomputer. However, such a computer is often put in a different place from the vibration experimental facility. Therefore, even in the case of not using the plurality of actuators, a hybrid experiment using the test device and the computer in remote places is necessary. However, in the technique disclosed in JP-A-60-13240 and U.S. Pat. No. 5,388,056 mentioned above, the computer for performing the numerical simulation is constituted so as to simultaneously control the actuators for the vibration test. This constitution is suitable for performing the test in one experimental facility. Thus, these conventional techniques do not consider the above theme.
Furthermore, the techniques disclosed in JP-A-9-79939 and JP-A-10-206304 mentioned above do not take into consideration a conception of actively varying command signals from the computer in accordance with responses such as the deformation and load of the test piece generated with vibration given by the actuator.
A hybrid experiment technique will be described below, taking as an example an evaluation of an earthquake resistance of a bridge shown in FIG. 2.
A bridge used for a highway or the like is equipped with a plurality of supporting structures each constituting a footing 102 on a ground 101 and a pier 103, and these supporting structures support an upper structure 105 via supporting members 104. A vibration response in the case that the piers are excited horizontally in the IIBxe2x80x94IIB section by earthquake acceleration will be evaluated in a hybrid experiment. Assuming that the whole of the bridges makes the same motion, a partial structure 201 corresponding to one span is drawn and then considered. This drawn structure 201 is divided into a part 202 to be used for numerical modeling and a part 203 to be used as an actual model.
A testing device has a construction as illustrated in FIG. 3. The actual model 203 (hereinafter referred to as a test piece) is fixed onto a base 301. A movable part of an actuator 303 fixed to a reaction wall 302 is connected with the test piece 203. In the connection between the actuator 303 and the test piece 203, a load cell 305 is so disposed that the reaction forces to the deformations applied by the actuator can be measured. The vibration generator 303 is so controlled as to reduce the difference between a feedback signal from a displacement measuring device (not illustrated), which is incorporated in the actuator, and a command value input to an actuator controller 304. A computer 306 has a numerical simulation block 23, a waveform generating block 32, and a measurement processing block 33. The computer 306 generates the input of the actuator controller 304 and outputs it to the actuator controller 304. To calculate this command value, the output of the load cell 305 is used.
The calculation of the command value is carried out by the computer 306, as follows. By the numerical simulation block 23, the computer 306 calculates a vibration response of the part 202 converted to a numerical modeling, using the following equation 1 of motion.                                                         [              M              ]                        ⁢                          {                                                                    d                    2                                    ⁢                  x                                                  d                  ⁢                                      xe2x80x83                                    ⁢                                      t                    2                                                              }                                +                                    [              C              ]                        ⁢                          {                                                ⅆ                  x                                                  ⅆ                  t                                            }                                +                                    [              K              ]                        ⁢                          {              x              }                                      =                              {            q            }                    +                      {            f            }                                              (        1        )            
where [M], [C], and [K] represent the respective matrices of mass, damping, and stiffness, {x} does a displacement vector, {q} does an external force vector caused by an earthquake, {f} does a reaction vector generated at a boundary point between the numerical and actual models.
In the displacement vector, the displacement of the portion corresponding to the boundary point between the numerical and actual models is used as a command value to apply a deformation to the test piece 203. If {q} and {f}, which correspond to external forces, are known, vibration response displacement vector {x} can be obtained by numerical integration at intervals of a minute time. For example, according to a centeral difference method, displacement vector {x}i+1 at time ti+1 can be obtained by the following equation 2, where suffix i indicates that the value is at time ti.                                           {            x            }                                i            +            1                          =                                            {                                                [                  M                  ]                                +                                                                            Δ                      ⁢                                              xe2x80x83                                            ⁢                      t                                        2                                    ⁡                                      [                    C                    ]                                                              }                                      -              1                                ⁢                      (                                                            [                  M                  ]                                ⁢                                  (                                                            2                      ⁢                                                                        {                          x                          }                                                i                                                              -                                                                  {                        x                        }                                                                    i                        -                        1                                                                              )                                            +                                                                                          Δ                      ⁢                                              xe2x80x83                                            ⁢                      t                                        2                                    ⁡                                      [                    C                    ]                                                  ⁢                                                      {                    x                    }                                                        i                    -                    1                                                              +                              Δ                ⁢                                  xe2x80x83                                ⁢                                                      t                    2                                    ⁡                                      (                                                                                            {                          q                          }                                                i                                            +                                                                        {                          f                          }                                                i                                            -                                                                        [                          K                          ]                                                ⁢                                                                              {                            x                            }                                                    i                                                                                      )                                                                        )                                              (        2        )            
{q}i necessary for this calculation is a test condition, so it has been stored in the computer or it is externally given in accordance with the progress of the test. For reaction force {f}i, the reaction force of the test piece 203 actually generated in the test is measured with the load cell 305. The output of the load cell 305 is properly processed by the measurement processing block 33 to be used as the reaction force {f}i. Besides, based on the processing result by the numerical simulation block 23, a time function of displacement to be applied to the test piece is calculated by the waveform generating block 32. The obtained function is output as command values.
That is, a vibration test process and a vibration response calculating process are simultaneously progressed in the following procedure: (1) reactive force {f}i is measured; (2) {x}i+1 is calculated by the equation 2 using external force {q}i and reaction force {f}i as external forces; (3) the obtained displacement at the boundary point between the numerical and actual models is applied to the test piece 203 with the actuator 305; and (4) the procedure is returned to step (1). By repeating the above steps, the vibration response of the whole structure can be evaluated by the vibration test with only one part.
In this technique, the computer 306 outputs control signals directly to the actuator controller 304. Therefore, the computer 306 must be disposed near the actuator 303 and the actuator controller 304. Besides, it is a necessary condition that the test piece reaction can accurately be measured. In the case of a vibration test using plural actuators, however, if some trouble has occurred in one actuator and as a result, the reaction of the corresponding test piece cannot be obtained, the test will end in failure though the other actuators are out of any trouble. In such a case, the whole expense of the test can be wasteful.
The present invention has been developed to solve the above-mentioned problems of the conventional techniques in a vibration testing device and a testing method for evaluating strength and reliability of a huge structure to, for example, an earthquake, and an object of the present invention is to provide a highly reliable vibration testing device in which one or more actuators are connected with a computer disposed in a remote place, and a method for evaluating a vibration response.
In order to achieve the above object, a first aspect of the present invention is directed to a vibration testing device constituting one or more actuator systems each including an actuator having a movable part for applying a deformation to a test piece, a control sensor for measuring a drive condition of the actuator, an actuator controlling device for controlling the drive condition of the actuator by the use of an input command signal and an output of the control sensor, and a monitoring sensor for measuring the response condition of the test piece and the drive condition of the actuator; and a computer system for outputting an command signal to each actuator system, wherein the computer system has a measurement processing block for inputting an output of the monitoring sensor and processing it so as to be able to be used in a parameter changing block; a model substituting block for modeling characteristics of the test piece vibrated in the actuator system by the use of a finite number of parameters, calculating a response quantity corresponding to the drive condition of the actuator, and then inputting the calculation result to a numerical simulation block and the parameter changing block; the parameter changing block for comparing the calculation result of the model substituting block with the processing result of the measurement processing block, and changing the parameter so that the actual characteristics of the test piece may substantially coincide with the characteristics of the test piece in the model substituting block; the numerical simulation block for calculating a vibration response at each interval of a preset time on the basis of a previously input structure numerical model, the processing result of the model substituting block, and a time function given as an external force applied to the structure; and a waveform generating block for calculating a time function of a deformation to be applied to the test piece on the basis of the result of the numerical simulation block, and outputting it as an instruction value to the actuator controlling device, whereby a series of processes of the model substitution, the numerical simulation and the waveform generation, and a series of processes of the measurement processing and the parameter change are repeatedly performed in parallel.
A second aspect of the present invention is directed to a method for evaluating a vibration response of a structure containing a main structure and one or more secondary structures connected thereto, constituting a numerical simulation processing step of calculating the vibration response at each interval of a preset time on the basis of a numerical model of the main structure, results of secondary structure model processing subsequently calculated, and a time function given as an external force applied to the structure; a secondary structure model processing step of modeling characteristics of the secondary structure by the use of a finite number of parameters and calculating a response quantity corresponding to a response of a portion interconnecting to the main structure; a test piece vibration processing step of vibrating a test piece for evaluating the characteristics of the secondary structure on the basis of the results of the numerical simulation processing to measure its response quantity; and a parameter change processing step of comparing the calculation results of the secondary structure model processing with the results of the test piece vibration processing, and successively changing a parameter so that the actual response of the test piece may substantially coincide with the response of the secondary structure in the secondary structure model processing, whereby the secondary structure model processing and the numerical simulation processing are repeatedly performed, and in parallel with this processing, the test piece vibration processing and the parameter change processing are repeatedly performed.
Other objects, features and advantages of the invention will become apparent from the following description of the embodiments of the invention taken in conjunction with the accompanying drawings.